Perfluorooctanoic acid induces liver and serum dyslipidemia in humanized PPARα mice fed an American diet.

Per- and polyfluoroalkyl substances (PFAS) are pervasive in the environment resulting in nearly universal detection in people. Human serum PFAS concentrations are strongly associated with increased serum low-density lipoprotein cholesterol (LDL-C), and growing evidence suggests an association with serum triacylglycerides (TG). Here, we tested the hypothesis that perfluorooctanoic acid (PFOA) dysregulates liver and serum triacylglycerides in human peroxisome proliferator activated receptor α (hPPARα)-expressing mice fed an American diet. Mice were exposed to PFOA (3.5 mg/L) in drinking water for 6 weeks resulting in a serum concentration of 48 ± 9 µg/ml. In male and female hPPARα mice, PFOA increased total liver TG and TG substituted with saturated and monounsaturated fatty acids. Lack of expression of PPARα alone also increased total liver TG, and PFOA treatment had little effect on liver TG in PPARα null mice. In hPPARα mice, PFOA neither significantly increased nor decreased serum TG; however, there was a modest increase in TG associated with very low-density cholesterol particles in both sexes. Intriguingly, in female PPARα null mice, PFOA significantly increased serum TG, with a similar trend in males. PFOA also modified fatty acid and TG homeostasis-related gene expression in liver, in a hPPARα-dependent manner, but not in adipose. The results of our study and others reveal the importance of context (serum concentration and genotype) in determining the effect of PFOA on lipid homeostasis.

Perfluorooctanoic acid activates multiple nuclear receptor pathways and skews expression of genes regulating cholesterol homeostasis in liver of humanized PPARα mice fed an American diet.

Humans are exposed to per- and polyfluoroalkyl substances (PFAS) in their drinking water, food, air, dust, and by direct use of consumer products. Increased concentrations of serum total cholesterol and low density lipoprotein cholesterol are among the endpoints best supported by epidemiology. The objectives of this study were to generate a new model for examining PFAS-induced dyslipidemia and to conduct molecular studies to better define mechanism(s) of action. We tested the hypothesis that perfluorooctanoic acid (PFOA) exposure at a human-relevant level dysregulates expression of genes controlling cholesterol homeostasis in livers of mice expressing human PPARα (hPPARα). Female and male hPPARα and PPARα null mice were fed a diet based on the "What we eat in America" analysis and exposed to PFOA in drinking water (8 µM) for 6 weeks. This resulted in a serum PFOA concentration of 48 µg/ml. PFOA increased liver mass, which was associated with histologically-evident lipid accumulation. Pooled analyses of serum lipoprotein cholesterol suggest that PFOA increased serum cholesterol, particularly in male mice. PFOA induced PPARα and constitutive androstane receptor target gene expression in liver. Expression of genes in four pathways regulating cholesterol homeostasis were also measured. PFOA decreased expression of Hmgcr in a PPARα-dependent manner. PFOA decreased expression of Ldlr and Cyp7a1 in a PPARα-independent manner. Apob expression was not changed. Sex differences were evident. This novel study design (hPPARα mice, American diet, long term exposure) generated new insight on the effects of PFOA on cholesterol regulation in the liver and the role of hPPARα.

Ambient toxicity due to chlorpyrifos and diazinon in a central California coastal watershed.

The Salinas River watershed along the central coast of California, U.S.A., supports rapidly growing urban areas and intensive agricultural operations. The river drains to an estuarine National Wildlife Refuge and a National Marine Sanctuary. The occurrence, spatial patterns, sources and causes of aquatic toxicity in the watershed were investigated by sampling four sites in the main river and four sites in representative tributaries during 15 surveys between September 1998 and January 2000. In 96 hr toxicity tests, significant Ceriodaphnia dubia mortality was observed in 11% of the main river samples, 87% of the samples from a channel draining an urban/agricultural watershed, 13% of the samples from channels conveying agricultural tile drain runoff, and in 100% of the samples from a channel conveying agricultural surface furrow runoff. In six of nine toxicity identification evaluations (TIEs), the organophosphate pesticides diazinon and/or chlorpyrifos were implicated as causes of observed toxicity, and these compounds were the most probable causes of toxicity in two of the other three TIEs. Every sample collected in the watershed that exhibited greater than 50% C. dubia mortality (n = 31) had sufficient diazinon and/or chlorpyrifos concentrations to account for the observed effects. Results are interpreted with respect to potential effects on other ecologically important species.

Acutei and chronic toxicity of nickel to marine organisms: implications for water quality criteria.

Acute and chronic toxicity tests were conducted to determine the effects of nickel on three U.S. west coast marine species: a fish (the topsmelt, Atherinops affinis), a mollusk (the red abalone, Haliotis rufescens), and a crustacean (the mysid, Mysidopsis intii). The 96-h median lethal concentration (LC50) for topsmelt was 26,560 microg/L, and the chronic value for the most sensitive endpoint in a 40-d exposure was 4,270 microg/L. The median effective concentration (EC50) for 48-h abalone larval development was 145.5 microg/L, and the chronic value for juvenile growth in a 22-d exposure through larval metamorphosis was 26.43 microgAL. The mysid 96-h LC50 was 148.6 microg/L, and the chronic value for the most sensitive endpoint in a 28-d, whole life-cycle exposure was 22.09 microg/L. The abalone and mysid acute values were lower than other values available in the literature. Acute-to-chronic ratios for nickel toxicity to the three species were 6.220, 5.505, and 6.727, respectively, which were similar to the only other available saltwater value of 5.478 (for Americamysis [Mysidopsis] bahia) and significantly lower than the existing values of 35.58 and 29.86 for freshwater organisms. Incorporation of data from the present study into calculations for water quality criteria would lower the criterion maximum concentration and raise the criterion continuous concentration for nickel.

An evaluation of methods for calculating mean sediment quality guideline quotients as indicators of contamination and acute toxicity to amphipods by chemical mixtures.

Mean sediment quality guideline quotients (mean SQGQs) were developed to represent the presence of chemical mixtures in sediments and are derived by normalizing a suite of chemicals to their respective numerical sediment quality guidelines (SQGs). Mean SQGQs incorporate the number of SQGs exceeded and the degree to which they are exceeded and are used for comparison with observed biological effects in the laboratory or field. The current research makes it clear, however, that the number and type of SQGs used in the derivation of these mean quotients can influence the ability of mean SQGQ values to correctly predict acute toxicity to marine amphipods in laboratory toxicity tests. To determine the optimal predictive ability of mean SQGQs, a total of 18 different chemical combinations were developed and compared. The ability of each set of mean SQGQs to correctly predict the presence and absence of acute toxicity to amphipods was determined using three independent databases (n = 605, 2753, 226). Calculated mean SQGQ values for all chemical combinations ranged from 0.002 to 100. The mean SQGQ that was most predictive of acute toxicity to amphipods is calculated as SQGQ1 = ((sigma ([cadmium]/4.21 )([copper]/270)([lead]/ 12.18)([silver]/1.77)([zinc]/ 410)([total chlordane]/6)([dieldrin]/8)([total PAHoc]/1,800)([total PCB]/400))/9). Both the incidence and magnitude of acute toxicity to amphipods increased with increasing SQGQI values. To provide better comparability between regions and national surveys, SQGQ1 is recommended to serve as the standard method for combination of chemicals and respective SQGs when calculating mean SQGQs.

Influence of sample manipulation on contaminant flux and toxicity at the sediment-water interface.

Toxicities of sediments from San Diego and San Francisco Bays were compared in laboratory experiments using sea urchin (Strongylocentrotus purpuratus) embryos exposed to pore water and at the sediment-water interface (SWI). Toxicity was consistently greater to embryos exposed at the SWI to intact (unhomogenized) sediment samples relative to homogenized samples. Measurement of selected trace metals indicated considerably greater fluxes of copper, zinc, and cadmium into overlying waters of intact sediment samples. Inhibition of sea urchin embryo development was generally greater in sediment pore waters relative to SWI exposures. Pore water toxicity may have been due to elevated unionized ammonia concentrations in some samples. The results indicate that invertebrate embryos are amenable to SWI exposures, a more ecologically relevant exposure system, and that sediment homogenization may create artifacts in laboratory toxicity experiments.

A large-scale categorization of sites in San Francisco Bay, USA, based on the sediment quality triad, toxicity identification evaluations, and gradient studies.

Sediment quality was assessed in San Francisco Bay, California, USA, using a two-tiered approach in which 111 sites were initially screened for sediment toxicity. Sites exhibiting toxicity were then resampled and analyzed for chemical contamination, recurrent toxicity, and, in some cases, benthic community impacts. Resulting data were compared with newly derived threshold values for each of the metrics in a triad-based weight-of-evidence evaluation. Sediment toxicity test results were compared with tolerance limits derived from reference site data, benthic community data were compared with threshold values for a relative benthic index based on the presence and abundance of pollution-tolerant and -sensitive taxa, and concentrations of chemicals and chemical mixtures were compared with sediment quality guideline-based thresholds. A total of 57 sites exceeded threshold values for at least one metric, and each site was categorized based on triad inferences. Nine sites were found to exhibit recurrent sediment toxicity associated with elevated contaminant concentrations, conditions that met program criteria for regulatory attention. Benthic community impacts were also observed at three of these sites, providing triad evidence of pollution-induced degradation. Multi- and univariate correlations indicated that chemical mixtures, heavy metals, chlordanes, and other organic compounds were associated with measured biological impacts in the Bay. Toxicity identification evaluations indicated that metals were responsible for pore-water toxicity to sea urchin larvae at two sites. Gradient studies indicated that the toxicity tests and benthic community metrics employed in the study predictably tracked concentrations of chemical mixtures in Bay sediments.

Evaluation and use of sediment toxicity reference sites for statistical comparisons in regional assessments.

Sediment reference sites were used to establish toxicity standards against which to compare results from sites investigated in San Francisco Bay (California, USA) monitoring programs. The reference sites were selected on the basis of low concentrations of anthropogenic chemicals, distance from active contaminant sources, location in representative hydrographic areas of the Bay, and physical features characteristic of depositional areas (e.g., fine grain size and medium total organic carbon [TOC]). Five field-replicated sites in San Francisco Bay were evaluated over three seasons. Samples from each site were tested with nine toxicity test protocols and were analyzed for sediment grain size and concentrations of trace metals, trace organics, ammonia, hydrogen sulfide, and TOC. The candidate sites were found to have relatively low concentrations of measured chemicals and generally exhibited low toxicity. Toxicity data from the reference sites were then used to calculate numerical tolerance limits to be used as threshold values to determine which test sites had significantly higher toxicity than reference sites. Tolerance limits are presented for four standard test protocols, including solid-phase sediment tests with the amphipods Ampelisca abdita and Eohaustorius estuarius and sea urchin Strongylocentrotus purpuratus embryo/larval development tests in pore water and at the sediment-water interface (SWI). Tolerance limits delineating the lowest 10th percentile (0.10 quantile) of the reference site data distribution were 71% of the control response for Ampelisca, 70% for Eohaustorius, 94% for sea urchin embryos in pore water, and 87% for sea urchins embryos exposed at the SWI. The tolerance limits are discussed in terms of the critical values governing their calculation and the management implications arising from their use in determining elevated toxicity relative to reference conditions.

Statistical significance of sediment toxicity test results: threshold values derived by the detectable significance approach.

A number of methods have been employed to determine the statistical significance of sediment toxicity test results. To allow consistency among comparisons, regardless of among-replicate variability, a protocol-specific approach has been used that considers protocol performance over a large number of comparisons. Ninetieth-percentile minimum significant difference (MSD) values were calculated to determine a critical threshold for statistically significant sample toxicity. Significant toxicity threshold values (as a percentage of laboratory control values) are presented for six species and nine endpoints based on data from as many as 720 stations. These threshold values are useful for interpreting sediment toxicity data from large studies and in eliminating cases where statistical significance is assigned in individual cases because among-replicate variability is small.

Sediment quality in Los Angeles Harbor, USA: a triad assessment.

Sediment quality in the Los Angeles and Long Beach Harbor area of southern California, USA, was assessed from 1992 to 1997 as part of the California State Water Resources Control Board's Bay Protection and Toxic Cleanup Program and the National Oceanic and Atmospheric Administration's National Status and Trends Program. The assessment strategy relied on application of various components of the sediment quality triad, combined with bioaccumulation measures, in a weight-of-evidence approach to sediment quality investigations. Results of bulk-phase chemical measurements, solid-phase amphipod toxicity tests, pore-water toxicity tests with invertebrate embryos, benthic community analyses (presented as a relative benthic index), and bioaccumulation measures indicated that inner harbor areas of this system are polluted by high concentrations of a mixture of sediment-associated contaminants and that this pollution is highly correlated with toxicity in laboratory experiments and degradation of benthic community structure. While 29% of sediment samples from this system were toxic to amphipods (Rhepoxynius abronius or Eohaustorius estuarius), 79% were toxic to abalone embryos (Haliotis rufescens) exposed to 100% pore-water concentrations. Statistical analyses indicated that amphipod survival in laboratory toxicity tests was significantly correlated with the number of crustacean species and the total number of species measured in the benthos at these stations. Triad measures were incorporated into a decision matrix designed to classify stations based on degree of sediment pollution, toxicity, benthic community degradation, and, where applicable, tissue concentrations in laboratory-exposed bivalves and feral fish.

Variability and reliability of real-time milk conductivity data.

The profile of milk conductivity values that were collected using an automated data acquisition system was evaluated for errant values. Conductivity values were recorded from 35 cows for three milkings. Conductivity values that were collected at 2-s intervals were extremely variable. They contained erroneously low values because of the nature of the electronic measuring system. The variability was reduced, but not eliminated, by increasing the interval to 6 s. Erroneously low values were removed by calculating a point estimate representing a mean of the 10 highest values recorded at 6-s intervals.

Electrical conductivity of reproductive tissue for detection of estrus in dairy cows.

The pattern of temporal measurements of electrical conductivity obtained from electrodes that had been surgically implanted in the mucosa of the vagina or in the submucosa of the vulva in each of five dairy cows was evaluated for changes associated with the occurrence of estrus. Tissue conductivity was monitored at 6-h intervals during and around estrus by hard-ware devices operating at either 16 or 100 kHz. Blood samples were taken at time of conductivity measurement for progesterone determination and at 2-h intervals during estrus for LH determination. Vaginal and vulvar biopsies were performed during diestrus and estrus to measure tissue hydration. Conductivity increased significantly at estrus relative to a nonestrus base period in both vaginal and vulvar tissue. Both electrical frequencies were found to be satisfactory for characterizing changes in tissue conductivity associated with estrus. Peak concentrations of luteinizing hormone, increases in tissue hydration, and patterns of blood progesterone were consistent with the occurrence of estrus during the time of elevated tissue conductivity.